As a putting aid, a target line is a path from a golf ball to a golf cup that, if followed, results in the ball landing in the cup. In order to properly envision the target line, it is helpful for a golfer to vertically align the golfer's line of sight with a vertical plane, which is perpendicular to a putting surface and passes through a centerline of the golf ball. If the golfer's line of sight is not aligned in this manner, it is less likely that the golfer will correctly envision the target line, and likely that the golfer will envision a line that does not lead the ball to the cup. If this occurs, and the remainder of the golfer's putting stroke is perfect, the ball will follow the improperly envisioned line, rather than the target line, and not land in the cup. However, even if the golfer properly envisions the target line, the ball can still miss the cup if a club face on the golfer's putter does not travel along the target line during the golfer's putting stroke. In addition, even if the golfer properly envisions the target line and swings the club face of the putter perfectly in line with the target line during the golfer's putting stroke, the ball can still miss the cup if the club face of the putter is not square to the ball when the club face contacts the ball. As a result, in order to develop an accurate and consistent putting stroke the golfer will find it helpful to combine each of the elements of properly aligning the golfer's line of sight over the target line, swinging the putter club face in line with the target line, and squaring the club face with the ball when the club face contacts the ball.
A number of devices exist for aiding a golfer in developing a more accurate and consistent putting stroke. However, many of these devices focus only on a single aspect of the putting stroke, typically in aiding the golfer in swinging the club face of the putter in line with the target line. As a result, these devices can actually hinder a golfer's putting ability by focusing on only one aspect of putting while ignoring others. In addition, many devices involve complicated designs that require sophisticated manufacturing or assembling techniques. Also, many devices are cumbersome and are not easily portable or compactable.